Architecture for high throughput semiconductor processing applications

ABSTRACT

A semiconductor wafer processing system in accordance with an embodiment of the present invention includes a loading station, a load lock, a process module, an intermediate process module, and a transport module which further includes a load chamber, a transfer chamber, and a pass-through chamber between the load chamber and the transfer chamber. The intermediate process module may be coupled to the load chamber, or both the load chamber and the transfer chamber. In one embodiment, the load lock is a single-wafer load lock capable of accommodating only a single wafer at a time to allow for fast pump down and vent cycles. In one embodiment, the pass-through chamber is configured as a cooling station to improve throughput for processes that require the wafer to be cooled in-between depositions, for example.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and incorporates by referenceU.S. Provisional Application No. 60/209,079, entitled “Wafer TransportAnd Processing System Architecture For High Throughput,” filed on Jun.2, 2000, by Craig L. Stevens and Karl B. Levy.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to semiconductor devicefabrication, and more particularly to semiconductor wafer processingsystems.

2. Description of the Background Art

Semiconductor wafer processing systems that have more than one moduleare referred to as “cluster tools.” Typically, a cluster tool has a loadlock module for receiving a semiconductor wafer, one or more processmodules for performing fabrication steps on the wafer, and a transportmodule for moving the wafer from the load lock module to a processmodule, and vice versa. Exemplary cluster tools are disclosed in U.S.Pat. No. 4,917,556 to Stark et al. and U.S. Pat. No. 5,186,718 to Tepmanet al., both of which are incorporated herein by reference in theirentirety.

The arrangement of modules in a semiconductor wafer processing system(i.e., the system's architecture) directly affects throughput.Throughput is an important performance measure of a semiconductor waferprocessing system because it is related to productivity the higher thethroughput, the more wafers that can be processed within a given amountof time. Accordingly, the cost of ownership of a semiconductor waferprocessing system and the fabrication cost per wafer depend onthroughput.

SUMMARY

The present invention relates to a method, system, and associatedapparatus for high throughput semiconductor processing applications. Theinvention may be used in a wide variety of semiconductor processingapplications including physical vapor deposition (PVD), chemical vapordeposition (CVD), etching, etc.

A semiconductor wafer processing system in accordance with an embodimentof the present invention includes a loading station, a load lock, aprocess module, an intermediate process module, and a transport modulewhich further includes a load chamber, a transfer chamber, and apass-through chamber between the load chamber and the transfer chamber.The intermediate process module is coupled to the load chamber; in oneembodiment, the intermediate process module is also coupled to thetransfer chamber.

In one embodiment, the load lock is a single-wafer load lock capable ofaccommodating only a single wafer at a time, and correspondingly has asmall volume which results in fast pump down and vent cycles.

In one embodiment, the load lock is capable of cooling a wafer during avent cycle. This eliminates the need to cool the wafer in a separatecooling station prior to returning the wafer to its cassette on theloading station.

In one embodiment, the pass-through chamber is configured as a coolingstation. For processes requiring the wafer to be cooled in-betweendepositions, the use of the pass-through chamber as a cooling stationimproves throughput by allowing the wafer to be cooled while it is intransit from a process module coupled to the transfer chamber to aprocess module coupled to the load chamber, for example.

These and other features and advantages of the present invention will bereadily apparent to persons of ordinary skill in the art upon readingthe entirety of this disclosure, which includes the accompanyingdrawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show perspective views of a semiconductor waferprocessing system in accordance with an embodiment of the presentinvention.

FIG. 2 shows a plan view of a semiconductor wafer processing system 100in accordance with an embodiment of the present invention.

FIG. 3 shows a side cross-sectional view of a load lock in accordancewith an embodiment of the present invention.

FIG. 4 shows a cross-sectional view of a degas module in accordance withan embodiment of the present invention.

FIG. 5 shows a cross-sectional view of a pass-through chamber configuredas a cooling station in accordance with an embodiment of the presentinvention.

FIG. 6 shows a perspective view of a process module in accordance withan embodiment of the present invention.

FIG. 7 shows a cross-sectional view of a process module configured forphysical vapor deposition in accordance with an embodiment of thepresent invention.

FIG. 8 shows a cross-sectional view of a process module configured forpre-clean in accordance with an embodiment of the present invention.

FIGS. 9A, 9B, 9C, and 9D show plan views of wafer processing systemsoptimized for running barrier/seed processes in accordance with anembodiment of the present invention.

FIGS. 10A and 10B show plan views of wafer processing systems optimizedfor running liner/barrier processes in accordance with an embodiment ofthe present invention.

DETAILED DESCRIPTION

FIGS. 1A and 1B show perspective views of a semiconductor waferprocessing system 100 in accordance with an embodiment of the presentinvention. Referring to FIG. 1A, system 100 includes a front-end module101 for interfacing with fabrication personnel or factory automationsystems, intermediate process modules 104 (i.e., 104A, 104B) and processmodules 103 (i.e., 103A, 103B, 103C, 103D, 103E, 103F, 103G) forperforming fabrication processing steps on wafers, and a transportmodule 102 for moving wafers between front end module 101 and othermodules of system 100. In one embodiment, system 100 is of the same typeas the INOVA XT 300 mm wafer processing system of Novellus Systems, Inc.of San Jose, Calif.

Typically, front-end module 101 is exposed to a clean room area of asemiconductor device fabrication facility, with the rest of system 100extending into a maintenance area. In the present embodiment, front-endmodule 101 protrudes out of a wall separating the clean room area andthe maintenance area. The entirety of system 100 may also be located ina single area, such as in a “ball room” configuration, for example.

Still referring to FIG. 1A, front-end module 101 includes a userinterface 110, loaders 115 (i.e. 115A, 115B), and an atmospheric robot201 shown in the plan view of FIG. 2. Fabrication personnel operatesystem 100 via user interface 110, which includes a keyboard/track-ball111 and a flat-panel display 112. System 100 is controlled using anetwork of computers (not shown) coupled to user interface 110. The useof computers to control a semiconductor wafer processing system, ingeneral, is known in the art and will not be further discussed here.That is, a person of ordinary skill in the art would know how to employa computer equipped with data acquisition and control cards to controlrobots, motors, actuators, transducers, gates, mass flow controllers,valves, interlocks, pumps, heaters, gas boxes, sensors, compressors,relays, and other control elements for use in a semiconductor waferprocessing system.

Front-end module 101 includes one or more loaders 115 for acceptingwafers to be processed. In the present embodiment, loaders 115 arefront-opening unified pods (FOUP) from Brooks Automation, Inc. ofChelmsford, Mass. System 100 may also employ any loader of the typegenerally used in the semiconductor industry including standardmechanical interface (SMIF) pods and cassette modules.

Transport module 102 includes one or more load locks 107 (107A shown inFIG. 1A, 107B shown in FIG. 1B), load chamber 116, transfer chamber 117,and a central pass-through chamber 106. The aforementioned components oftransport module 102 are depicted in FIGS. 1A and 1B with their topcovers removed for illustration purposes. As can be appreciated, thecomponents of transport module 102 may be manufactured as a singleintegrated module, or as separate, detachable modules. Each processmodule 103 is attached to either load chamber 116 or transfer chamber117 via a wafer transfer port, which may be MESC-compatible per SEMIspecifications. Each intermediate process module 104 is also similarlyattached to load chamber 116 and transfer chamber 117. In someembodiments, an intermediate process module 104 is attached to loadchamber 116, but not to transfer chamber 117.

Load locks 107 buffer the inner modules of system 100 from atmosphericpressure, thereby allowing system 100 to perform what is commonly knownas “continuous processing.” That is, the inner modules of system 100 canprocess wafers without having to undergo pump down and vent cycles. Thiscapability of system 100 is now discussed with reference to FIG. 2. Eachload lock 107 has an opening 301 (i.e., 301A, 301B) facing atmosphericrobot 201 and an opening 302 (i.e., 302A, 302B) facing vacuum robot202A. To receive a wafer from atmospheric robot 201, opening 301 isopened while opening 302 remains closed. Atmospheric robot 201 thenplaces a wafer in the load lock 107. Thereafter, opening 301 is closedand the load lock 107 is pumped down using a vacuum pump. When thepressure in the load lock 107 is equalized to the pressure in loadchamber 116 (which in normal operation is under vacuum), opening 302 isopened to allow vacuum robot 202A to remove the wafer and replace itwith another wafer. Opening 302 is then closed, and the load lock 107 isvented to atmospheric pressure. A vent gas such as helium may beintroduced into the load lock 107 to facilitate venting. As will befurther discussed below, a wafer can also be cooled in the load lock 107during the vent cycle. Once the load lock 107 is vented, opening 301 isopened to allow atmospheric robot 201 to pick up the wafer from the loadlock 107. As is evident from the foregoing, the modules of system 100forward of opening 302 are not exposed to atmospheric pressure duringnormal operation, and can thus continually accept wafers from the loadlocks 107 without having to be vented and pumped down.

FIG. 3 shows a side cross-sectional view of a load lock 107. Becauseload locks 107A and 107B are mirror images of one another, the followingdiscussion equally applies to both load locks. As shown in FIG. 3, aload lock 107 includes a wafer support in the form of a pedestal 303. Inthis embodiment, the load lock 107 is a single-wafer load lock, and thushas a single pedestal 303 for supporting only one wafer at a time.Because the load lock 107 only needs to accommodate a single wafer, theload lock 107 has a correspondingly small volume, which improves thethroughput of system 100 by allowing for fast pump down and vent cycles.

A wafer entering the load lock 107 from either of its openings is firstplaced on top of pins 304, which protrude through holes (not shown) inpedestal 303. An air cylinder 305 is coupled to a pedestal lift 306,which in turn is fixedly attached to pedestal 303. Actuating aircylinder 305 moves pedestal lift 306 and pedestal 303 in the verticaldirection. Bellows assembly 309 maintains a vacuum seal around pedestallift 306. To support the wafer on pedestal 303 during a pump down orvent cycle, pedestal 303 is transitioned to the up position, therebylifting the wafer from pins 304. At the end of the pump down or ventcycle, pedestal 303 is transitioned to the down position to lower thewafer back on pins 304. From pins 304, the wafer is picked up by arobot.

While on pedestal 303, the wafer can be cooled by flowing a coolant inan embedded channel 307. In this embodiment, water at a temperature of20° C. is flown in channel 307 via port 308 to cool a newly processedwafer during a vent cycle. This improves the throughput of system 100 byeliminating the need to move the wafer to a separate cooling stationprior to moving the wafer back to its cassette on a loader 115.

A wafer may also be heated while on pedestal 303 by flowing heatedliquid in embedded channel 307 or, alternatively, by activating heatingelements such as resistors embedded in pedestal 303. The wafer may alsobe heated inside the load lock 107 using other techniques including byradiation (e.g., using a lamp array). For fabrication processesrequiring the wafer to be pre-heated to a certain temperature prior toprocessing, heating the wafer in the load lock 107 during pump downfurther improves throughput by eliminating the need to pre-heat thewafer in a separate heating station or in a process module.

Still referring to FIG. 3, a pump 310 (e.g., a turbo pump) is used topump down the load lock 107 to vacuum after the load lock is roughedthrough a foreline coupled to foreline valve 321. A gate valve 311isolates load lock 107 from pump 310 during a vent cycle. In accordancewith conventional nomenclature, the term “vacuum” is used in the presentdisclosure to refer to some low pressure suitable for semiconductorprocessing, and does not necessarily mean zero pressure. Of course, thespecific operating pressures of a load lock 107 and other modules ofsystem 100 depend on specific process requirements.

Besides those disclosed herein, other suitable pedestals, load locks,and techniques for cooling and heating a wafer inside a load lock thatmay also be employed in the present invention are disclosed in thefollowing commonly-assigned disclosures, which are incorporated hereinby reference in their entirety: U.S. patent application Ser. No.09/346,258, entitled “Wafer Processing Architecture For MaximumThroughput”, filed on Jun. 30, 1999; U.S. patent application Ser. No.09/409,841, entitled “Wafer Processing Architecture Including LoadLocks”, filed on Sep. 30, 1999; and U.S. patent application Ser. No.09/635,998, entitled “Apparatus and Method For Semiconductor WaferCooling, Heating, And Backside Particle Control”, filed on Aug. 9, 2000.

As shown in FIG. 2, system 100, in one embodiment, includes intermediateprocess modules 104 (i.e. 104A, 104B) that are accessible from loadchamber 116 and transfer chamber 117. Each intermediate process module104 has an opening 401 (i.e., 401A, 401B) facing load chamber 116 and anopening 402 (i.e., 402A, 402B) facing transfer chamber 117. Openings 401and 402 have isolation valves, such as slit valves or gate valves, thatcan be closed to isolate the intermediate process module 104 from therest of system 100 during wafer processing. In some embodiments, anintermediate process module 104 has an opening 401, but no opening 402.

An intermediate process module 104 is used for performingpre-processing, post-processing, or processing steps on a wafer. In oneembodiment, an intermediate process module 104 is configured as a degasmodule, which removes adsorbed water from a wafer by heating. Referringto FIG. 4, there is shown a cross-sectional view of an exemplaryintermediate process module 104 configured as a degas module. The degasmodule of FIG. 4 includes an opening 401 (not shown) and, optionally, anopening 402 (not shown) for allowing a wafer to be placed in and removedfrom the degas module. A hot pedestal 403 supports and heats thebackside of the wafer, while a top heater 404 heats the top or activeside of the wafer. The wafer may be heated using a variety of heatingtechniques including by activating heating elements embedded in hotpedestal 403 and top heater 404. Thermocouple assemblies 405 are coupledto hot pedestal 403 and top heater 404 to monitor their temperatures. Inone embodiment, the outputs of thermocouple assemblies 405 are coupledto a heater control unit (not shown) which regulates the temperatures ofhot pedestal 403 and top heater 404. To facilitate wafer heating, heliumis introduced into the chamber of the degas module at a pressure ofapproximately 10 Torr; after the wafer is heated, the degas chamber ispumped back down to a pressure approximately equal to that of loadchamber 116 or transfer chamber 117 depending on the wafer transferpath.

A throttle valve 408 between a chamber 409 and a turbo pump 406regulates the evacuation rate of chamber 409 during pump downs. A gatevalve 407 isolates turbo pump 406 from chamber 409 during vent cycles.Besides the degas module of FIG. 4, other modules for heating a wafermay also be used as a degas module. For example, in one embodiment, thedegas module is of the same type as that offered by Novellus Systems,Inc. for its INOVA XT 300 mm wafer processing system.

As shown in FIG. 2, central pass-through chamber 106 is located betweenload chamber 116 and transfer chamber 117. In one embodiment,pass-through chamber 106 is configured as a cooling station for coolinga wafer in-between processing steps. As will be further discussed lateron below, this improves the throughput of system 100 by reducing thetime spent on cooling the wafer in a process module 103. FIG. 5 shows across-sectional view of an exemplary pass-through chamber 106 configuredas a cooling station. The cooling station of FIG. 5 has shelves 501 forcooling a wafer, and shelves 502 for cooling another wafer. Of course,the number of shelves incorporated in the cooling station depends onspecific requirements. The middle section of the cooling station,labeled as area 503, has enough space to allow a robot arm to bepositioned underneath a wafer to pick it up. Similarly, there is enoughspace for the robot arm to lower a wafer on shelves 501 or 502, and thenretract. A handle 504 is provided for conveniently lifting off top cover507 during maintenance, for example. In this embodiment, wafers arecooled by circulating a coolant such as water in embedded coolingchannel 506 via coolant inlet 505 (a corresponding coolant outlet is notshown). In lieu of the cooling station of FIG. 5, other types of wafercooling stations may also be used as a pass-through chamber 106.

In some embodiments, an isolation valve (e.g., see isolation valve 901of FIGS. 9B, 9C, 9D, 10A, and 10B) is placed between load chamber 116and transfer chamber 117. This allows the modules attached to transferchamber 117 (the “back-end” of system 100) to be isolated from themodules attached to load chamber 116 (the “front-end” of system 100).Isolating load chamber 116 from transfer chamber 117 allows processmodules running incompatible or contamination-sensitive processes to be15, separated. In systems 100 with an isolation valve between the loadand transfer chambers (e.g., the systems 100 of FIGS. 9B, 9C, 9D, 10A,and 10B), the intermediate process modules 104 are not equipped withopenings 402 facing transfer chamber 117.

In some embodiments, transfer chamber 117 is equipped with a vacuum unitcapable of pumping down transfer chamber 117 to either high pressure orlow pressure.

This capability is commonly referred to as “Hi-Lo,” and is employed whenthe mix of modules attached to transfer chamber 117 includes highpressure and low pressure modules. For example, chemical vapordeposition (CVD) modules typically operate at high pressures (e.g.,0.5–200 Torr), whereas physical vapor deposition (PVD) modules operateat lower pressures (e.g., ˜10⁻⁷ Torr transfer pressure; 0.5–20×10⁻³ Torrprocess pressure). In that case, the CVD and PVD modules are attached totransfer chamber 117, and an isolation valve is installed betweentransfer chamber 117 and load chamber 116. Pumping down (or venting)transfer chamber 117 to a relatively high pressure with the isolationvalve closed allows the chamber of a CVD module to be exposed totransfer chamber 117. Similarly, transfer chamber 117 is pumped down toa relatively low pressure to allow the chamber of a PVD module to beexposed to transfer chamber 117.

As mentioned, system 100 also includes process modules 103 that areattached to either load chamber 116 or transfer chamber 117. A processmodule 103 includes a chamber for performing pre-processing,post-processing, or processing steps on a wafer. The general mechanicalconfiguration of an exemplary process module 103 is now described withreference to the perspective view of FIG. 6. As shown in FIG. 6, thecomponents of the process module 103 are supported by a frame 601. Theprocess module 103 is attached to either load chamber 116 or transferchamber 117 via a wafer transfer port 602, which is MESC-compatible inthis embodiment. Typically, a robot arm enters a chamber 603 via thewafer transfer port 602, and places the wafer on an electrostatic chuck604. Other types of wafer supports may also be used in lieu of anelectrostatic chuck.

As depicted in FIG. 6, a source 605 is lifted over chamber 603 using ahoist assembly 606. Hoist assembly 606 conventionally lowers and liftssource 605 for maintenance purposes, for example. In normal operation,source 605 covers chamber 603 and forms a vacuum seal therewith. A pump607 pumps down chamber 603 to a pressure suitable for wafer processing.Also shown in FIG. 6 is an operator's panel 608 for manually actuatingthe components (e.g., hoist assembly, emergency stop circuit) of theprocess module 103, and a control electronics assembly 609 coupled tothe computer network (not shown) of system 100. Electronics assembly 609includes circuitry for data acquisition and control, interlockmonitoring, and computer interfacing. Source 605 can be any type ofsource used in the semiconductor industry including those used forphysical vapor deposition (PVD) or chemical vapor deposition (CVD).

FIG. 7 shows a cross-sectional view of an exemplary process module 103configured for PVD. Shown in FIG. 7 is a PVD module without its source.In one 1 embodiment, the source of the PVD module is a hollow cathodemagnetron source of the same type as that disclosed in U.S. Pat. No.6,179,973, entitled “Apparatus And Method For Controlling PlasmaUniformity Across A Substrate,” incorporated herein by reference in itsentirety. The just-mentioned patent is assigned to Novellus Systems,Inc., which is also the assignee of the present disclosure. The sourcefor the PVD module of FIG. 7 may also be a planar magnetron source.Referring to FIG. 7, the PVD module includes pins 702 for supporting awafer being transferred. Pins 702 protrude through an electrostaticchuck 701 that is movable in the vertical direction (using a liftingmechanism similar to that of pedestal 303 of a load lock 107, forexample). To place a wafer in the PVD module for processing, a robot armenters chamber 707 and places the wafer on pins 702. Thereafter,electrostatic chuck 701 is transitioned to the up position, therebylifting the wafer from pins 702. After processing, electrostatic chuck701 is transitioned to the down position to lower the wafer back on pins702, where the robot arm can pick-up and remove the newly processedwafer from the PVD module.

Electrostatic chuck 701 supports the wafer during processing, andprevents the wafer from moving by clamping it with electrostatic force.The temperature of electrostatic chuck 701 (and thus the approximatetemperature of the wafer resting on it) is monitored using athermocouple assembly 705. To regulate the temperature of electrostaticchuck 701, a coolant such as water is circulated in embedded coolingchannels (not shown) coupled to coolant inlet 706 (a correspondingcoolant outlet is not shown). Other mechanisms for supporting andholding a wafer may also be used in lieu of the electrostatic chuck.Still referring to FIG. 7, a cryo pump 703 pumps down chamber 707 to apressure suitable for sputtering. A gate valve 704 allows chamber 707 tobe isolated from cryo pump 703.

In one embodiment, PVD and CVD modules of the same type as that offeredby Novellus Systems, Inc. for its INOVA XT 300 mm wafer processingsystem are used as process modules 103. For example, modules availablefrom Novellus Systems, Inc. for depositing tantalum (Ta), copper (Cu),titanium (Ti), titanium nitride (TiN), aluminum, and various dielectric,metal, adhesion, and barrier materials on a wafer are suitable for usein the present invention.

FIG. 8 shows a cross-sectional view of an exemplary process module 103configured for running a “pre-clean” process. Generally speaking, apre-clean process prepares a wafer for sputtering or chemical vapordeposition by removing a thin layer (e.g., ˜200 Angstroms) from the topsurface of the wafer. The removed layer may be a contact surface, a viabottom surface, or film deposited on the wafer, for example. Shown inFIG. 8 is a pre-clean module without its source. Similar to the PVDmodule of FIG. 7, the pre-clean module has pins 801 for supporting awafer being transferred. Pins 801 protrude through an electrostaticchuck 802, which supports and holds the wafer during processing.Electrostatic chuck 802 is movable in the vertical direction using alifting mechanism similar to that of pedestal 303 of a load lock 107.The temperature of electrostatic chuck 802 is regulated by circulatingcoolant in embedded cooling channels (not shown) coupled to coolantinlet 803 and coolant outlet 804. An optical probe assembly 805 monitorsthe temperature of the wafer being processed by pyrometry. In oneembodiment, optical probe assembly 805 is an in-situ wafer temperaturemonitor from Cl Systems of Israel.

Still referring to FIG. 8, a turbo pump 806, which is coupled to chamber810 through a gate valve 807, pumps down chamber 810 to a pressuresuitable for wafer processing. A radio frequency (RF) matching unit 808matches the characteristic impedance of the pedestal and low frequencyplasma in chamber 810 to the output impedance of an RF generatorsupplying RF power to the pre-clean module via connector 809.

In one embodiment, the pre-clean module is of the same type as thatoffered by Novellus Systems, Inc. for its INOVA XT 300 mm waferprocessing system.

It is to be noted that a process module 103 may be configured to beother than a PVD module or pre-clean module discussed above. Forexample, a process module 103 may also be configured as a chemical vapordeposition module, a degas module, or a cooling station.

The general operation of a system 100 is now described with reference toFIG. 2. A cassette containing wafers to be processed is manually loadedby fabrication personnel on a loader 115 (115A or 115B). Of course, withthe appropriate loader, system 100 may also accept wafers from anautomated guided vehicle (AGV) or other factory automation system, forexample. Atmospheric robot 201, which may be an atmospheric robot fromBrooks Automation, Inc., picks up a wafer from the cassette and movesthe wafer to a load lock 107 (107A or load lock 107B, whichever isavailable). A vacuum robot 202A in load chamber 116 picks up the waferfrom the load lock 107 and, depending on the fabrication process to beperformed, moves the wafer to process module 103A, process module 103G,intermediate process module 104A, intermediate process module 104B, orpass-through chamber 106. Depending on the fabrication process, thewafer reaches transfer chamber 117 through intermediate process module104A, intermediate process module 104B, or pass-through chamber 106. Avacuum robot 202B then picks up and moves the wafer to a process moduleattached to transfer chamber 117. Vacuum robots 202A and 202B are vacuumrobots of the type generally used in the semiconductor industry such asthose available from Brooks Automation, Inc. Depending on thefabrication process, the wafer may go through any module attached toload chamber 116 and/or transfer chamber 117 on its way back to itscassette on the loader 115 via a load lock 107 (107A or 107B, whicheveris available). To improve throughput, the wafer is cooled in the loadlock 107 while the load lock 107 is vented to atmosphere.

In another aspect of the present invention, the arrangement of modulesof a system 100 is optimized to minimize the number of wafer transfers,and thereby improve throughput. Specifically, in the following modulearrangements and wafer transfer paths, the modules are strategicallylocated to balance the processing load of a system 100 for a given typeof process. Of course, the present invention is not limited to theaforementioned module arrangements; a person of ordinary skill havingthe benefit of this disclosure will be able to come up with alternative,equivalent arrangements. Further, while the following wafer transferpaths are described using a single wafer as an example, the presentinvention is not so limited and may be used to process multiple wafersat the same time.

FIGS. 9A, 9B, 9C, and 9D show plan views of systems 100 optimized fordepositing copper barrier and seed layers on a wafer for coppermetallization. Table 1 summarizes the wafer transfer path for the system100 of FIG. 9A.

TABLE 1 WAFER TRANSFER PATH FOR THE SYSTEM OF FIG. 9A (1) LoadingStation 115A or 115B (2) Load Lock 107A or 107B (3) Degas Module(Intermediate Process Module 104A or 104B) (4) Pre-Clean (Process Module103B or 103F) (5) PVD Tantalum (Process Module 103C or 103E) (6) Coolingin Pass-Through Chamber (Central Pass-Through Chamber 106) (7) PVDCopper (Process Module 103A or 103G) (8) Load Lock 107A or 107B (9)Loading Station 115A or 115B (wherever the wafer's cassette is)

Referring to FIG. 9A and Table 1, a wafer is transferred from itscassette on a loading station 115 to a load lock 107 (either 107A or107B, whichever is available). Once the wafer is in the load lock 107,the load lock 107 is sealed and pumped down to approximately the samepressure as that of load chamber 116. Thereafter, the wafer istransferred from the load lock 107 to an intermediate process module 104(either 104A or 104B, whichever is available), which is configured as adegas module for removing adsorbed water from the wafer. In oneembodiment, the wafer is heated in the degas module to a temperaturegreater than 300° C. Thereafter, the wafer is transferred to processmodule 103B or 103F, each of which is configured as a pre-clean modulefor preparing the surface of the wafer prior to depositing a layer ofcopper barrier material, such as tantalum, thereon. In the example ofFIG. 9A, each intermediate process module 104 configured as a degasmodule has an opening facing load chamber 116 and another opening facingtransfer chamber 117. This allows the wafer to be loaded into theintermediate process module 104 using the vacuum robot in load chamber116, and be picked up from the intermediate process module 104 by thevacuum robot in transfer chamber 117. As can be appreciated, throughputis thereby improved because the wafer is transferred from the front-end,to a degas module, and then directly to a pre-clean module in theback-end without having to stop at a separately located wafer hand-offlocation.

Still referring to FIG. 9A and Table 1, the wafer is transferred fromthe pre-clean module to process module 103C or 103E, each of which isconfigured as a PVD module for depositing tantalum or tantalum nitrideon the wafer. The tantalum acts as a barrier layer to prevent asubsequently deposited copper layer from migrating into the dielectriclayer. From the PVD tantalum module, the wafer is then transferred tothe pass-through chamber 106 configured as a cooling station. There, thewafer is cooled prior to being transferred to process module 103A or103G, each of which is configured as a PVD module for depositing acopper seed layer on the wafer. The use of pass-through chamber 106 as acooling station allows the wafer to be cooled on its way from the PVDtantalum module in the back-end to the PVD copper module in thefront-end, thereby improving throughput by reducing the time spentcooling the wafer in the aforementioned PVD modules. Cooling the waferto a temperature less than 100° C. after the tantalum deposition andprior to copper deposition has been found to minimize grain size (forlower resistivity) and to decrease agglomeration. An alternativetechnique for achieving the just mentioned advantages would be to coolthe wafer for 35 seconds in the PVD tantalum module after tantalumdeposition and then to cool the wafer for 15 seconds in the PVD coppermodule prior to copper deposition. Using the pass-through chamber 106 tocool the wafer on its way from the back-end to the front-end of system100 reduces the total cooling time in the PVD modules by approximately10 seconds in some instances. This allows the PVD modules to spend mostof their time depositing materials on the wafers, rather than coolingthem.

As shown in Table 1, the wafer is transferred from the PVD copper moduleto a load lock 107 (107A or 107B, whichever is available). The wafer iscooled in the load lock 107 while the load lock is being vented toatmosphere. This further improves throughput by eliminating the need tocool the wafer in a separate cooling station prior to returning thewafer to its cassette. After the load lock 107 is vented to atmosphere,the opening of the load lock 107 facing the loading station 115 isopened to allow an atmospheric robot to pick-up the wafer and return itto its cassette on the loading station 115.

In one embodiment, the process disclosed in commonly-assigned U.S.application Ser. No. 09/491,853, filed on Jan. 26, 2000, by ErichKlawuhn, Kwok Fai Lai, Patrick Rymer, Maximillian, Biberger, Karl Levy,and Kaihan Ashtiani is used in conjunction with the wafer transfer pathof Table 1. Of course, the wafer transfer path of Table 1, and all otherwafer transfer paths in the present disclosure, is not limited to anyspecific set of process parameters. For example, other processes fordegassing, pre-cleaning, tantalum and tantalum nitride deposition, andcopper deposition commonly used in the semiconductor industry may alsobe employed in the modules specified in Table 1.

The system 100 of FIG. 9B and wafer transfer path of Table 2 illustrateanother way of depositing copper barrier and seed layers on a wafer inaccordance with an embodiment of the present invention; in the system100 of FIG. 9B, a CVD based barrier is used instead of a PVD basedbarrier. Unlike the system 100 of FIG. 9A, the system 100 of FIG. 9B hasan isolation valve 901 for isolating load chamber 116 from transferchamber 117. As mentioned, isolation valve 901 is employed to separateprocess modules running incompatible or contamination-sensitiveprocesses. Similarly, the systems 100 of FIGS. 9C, 9D, 10A, and 10B havean isolation valve 901, and intermediate transfer modules 104 that donot open to transfer chamber 117.

TABLE 2 WAFER TRANSFER PATH FOR THE SYSTEM OF FIG. 9B (1) LoadingStation 115A or 115B (2) Load Lock 107A or 107B (3) Degas Module(Intermediate Process Module 104A or 104B) (4) Central Pass-ThroughChamber 106 (Hand-off only) (5) Pre-Clean (Process Module 103B or 103F)(6) CVD Titanium Nitride (Process Module 103C or 103E) (7) CentralPass-Through Chamber 106 (Cooling) (8) PVD Tantalum (Process Module103A) (9) PVD Copper (Process Module 103G) (10) Load Lock 107A or 107B(11) Loading Station 115A or 115B (wherever the wafer's cassette is)

Referring to FIG. 9B and Table 2, a wafer is transferred from a loadingstation 115, to a load lock 107, and then to a degas module(intermediate process modules 104A or 104B). From the degas module, thewafer is transferred to the back-end by opening isolation valve 901 andplacing the wafer in pass-through chamber 106. Isolation valve 901 isthen closed. (Note that isolation valve 901 is opened and closed toallow a wafer to be transferred from the front-end to the back-end, andvice versa.) In transferring the wafer from the front-end to theback-end, pass-through chamber 106 is used only as a hand-off location.Accordingly, the wafer is immediately transferred from pass-throughchamber 106 to a pre-clean module (process module 103B or 103F) in theback-end.

In the system 100 of FIG. 9B, transfer chamber 117 is capable of Hi-Looperation for operating transfer chamber 117 at high pressure whenisolation valve 901 is closed and the chamber of a CVD titanium nitridemodule is open, and at low pressure when isolation valve 901 is open andtransfer chamber 117 is exposed to load chamber 116 (which has PVDcopper and tantalum modules attached thereto). After preparing thesurface of the wafer at the pre-clean module, the wafer is transferredto a CVD titanium nitride module (process module 103C or 103E). There, alayer of titanium nitride, which is a barrier for subsequently depositedcopper layer, is deposited on the wafer by CVD. From the CVD titaniumnitride module, the wafer is cooled in pass-through chamber 106 and thentransferred to a PVD tantalum module (process module 103A) in thefront-end to deposit tantalum on the wafer. Thereafter, a copper seedlayer is deposited on the wafer in a PVD copper module (process module103G). In the system 100 of FIG. 9B, the wafer is cooled in the PVDtantalum module after the tantalum deposition, and in the PVD coppermodule prior to the deposition of the copper seed layer. From the PVDcopper module, the wafer is cooled in a load lock 107, and transferredback to its cassette on the loading station 115.

The system 100 of FIG. 9C and wafer transfer path of Table 3 illustrateanother way of depositing copper barrier and seed layers on a wafer inaccordance with an embodiment of the present invention. As shown in FIG.9C and Table 3, a wafer is transferred from a loading station 115, to aload lock 107, and then to a degas module (intermediate process module104A or 104B). From the degas module, the surface of the wafer isprepared in a pre-clean module (process module 103A or 103G).Thereafter, the wafer is transferred to the back-end by placing thewafer in pass-through chamber 106. In the system 100 of FIG. 9C,pass-through chamber 106 is only used as a hand-off location fortransferring the wafer between load chamber 116 and transfer chamber117. Further, transfer chamber 117 in this embodiment is capable ofHi-Lo operation. From pass-through chamber 106, the wafer is transferredto a CVD barrier module (process module 103C or 103D) in the back-endfor deposition of a titanium nitride layer. From the CVD barrier module,the wafer is optionally transferred to a PVD tantalum module (processmodule 103E) where a barrier layer of tantalum is deposited on the waferusing a PVD process. After the PVD of tantalum, the wafer is transferredto a PVD copper module (process module 103F) for deposition of a copperseed layer using a PVD process. The wafer is cooled between the PVD oftantalum and the PVD of copper. Thereafter, another copper layer isoptionally deposited on the wafer using a CVD process in a CVD coppermodule to obtain a continuous seed (seed repair) (process module 103B).From the CVD copper module, the wafer is transferred to pass-throughchamber 106 for hand-off, and then transferred back to its cassette onthe loading station 115 via a load lock 107. The wafer is cooled in theload lock 107 while the load lock is vented to atmosphere.

TABLE 3 WAFER TRANSFER PATH FOR THE SYSTEM OF FIG. 9C (1) LoadingStation 115A or 115B (2) Load Lock 107A or 107B (3) Degas Module(Intermediate Process Module 104A or 104B) (4) Pre-Clean (Process Module103A or 103G) (5) Central Pass-Through Chamber 106 (Hand-off only) (6)CVD Barrier (Process Module 103C or 103D) (7) PVD Tantalum (ProcessModule 103E) (Optional) (8) PVD Copper (Process Module 103F) (9) CVDCopper (Process Module 103B) (Optional) (10) Central Pass-ThroughChamber 106 (Hand-off only) (11) Load Lock 107A or 107B (12) LoadingStation 115A or 115B (wherever the wafer's cassette is)

The system 100 of FIG. 9D and wafer transfer path of Table 4 illustrateanother way of depositing copper barrier and seed layers on a wafer inaccordance with an embodiment of the present invention. Referring toFIG. 9D and Table 4, a wafer is transferred from a loading station 115,to a load lock 107, and then to a degas module (intermediate processmodule 104A or 104B). From the degas module, the surface of the wafer isprepared in a pre-clean module (process module 103A or 103G).Thereafter, the wafer is transferred to the back-end by placing thewafer in pass-through chamber 106. In the system 100 of FIG. 9D,pass-through chamber 106 is only used as a hand-off location fortransferring the wafer between load chamber 116 and transfer chamber117, and accordingly is not configured as a cooling station. Further,transfer chamber 117 in this embodiment is capable of Hi-Lo operation.From pass-through chamber 106, the wafer is transferred to a CVD barriermodule (process module 103B or 103C) in the back-end for deposition of aCVD based barrier. From the CVD barrier module, the wafer is transferredto a CVD copper module for deposition of a copper seed layer (processmodule 103E or 103F). From the CVD copper module, the wafer istransferred to pass-through chamber 106 for hand-off, and transferredback to its cassette on the loading station 115 via a load lock 107. Thewafer is cooled in the load lock 107 while the load lock is vented toatmosphere.

TABLE 4 WAFER TRANSFER PATH FOR THE SYSTEM OF FIG. 9D (1) LoadingStation 115A or 115B (2) Load Lock 107A or 107B (3) Degas Module(Intermediate Process Module 104A or 104B) (4) Pre-Clean (Process Module103A or 103G) (5) Central Pass-Through Chamber 106 (Hand-off only) (6)CVD Barrier (Process Module 103B or 103C) (7) CVD Copper (Process Module103E or 103F) (8) Central Pass-Through Chamber 106 (Hand-off only) (9)Load Lock 107A or 107B (10) Loading Station 115A or 115B (wherever thewafer's cassette is)

FIGS. 10A and 10B show plan views of systems 100 optimized fordeposition of an adhesion layer of titanium and a barrier layer oftitanium nitride. Referring to the system 100 of FIG. 10A and the wafertransfer path of Table 5, a wafer is transferred from a loading station115, to a load lock 107, and then to a degas module (intermediateprocess module 104A or 104B). From the degas module, the surface of thewafer is prepared in a pre-clean module (process module 103A or 103G).Thereafter, the wafer is transferred to the back-end by placing thewafer in pass-through chamber 106. In the system 100 of FIG. 10A,pass-through chamber 106 is only used as a hand-off location fortransferring the wafer between load chamber 116 and transfer chamber117, and accordingly is not configured as a cooling station. Frompass-through chamber 106, the wafer is transferred to a PVDtitanium/titanium nitride module (process module 103B, 103C, or 103F) inthe back-end. There, a layer of titanium (e.g., ˜250 Angstroms) isdeposited on the wafer by PVD. While still in the PVD titanium/titaniumnitride module, a layer of titanium nitride (e.g., ˜500 Angstrom) isdeposited on the wafer also by PVD. From the PVD titanium/titaniumnitride module, the wafer is transferred to pass-through chamber 106 forhand-off, and transferred back to its cassette on the loading station115 via a load lock 107. The wafer is cooled in the load lock 107 whilethe load lock is vented to atmosphere.

TABLE 5 WAFER TRANSFER PATH FOR THE SYSTEM OF FIG. 10A (1) LoadingStation 115A or 115B (2) Load Lock 107A or 107B (3) Degas Module(Intermediate Process Module 104A or 104B) (4) Pre-Clean (Process Module103A or 103G) (5) Central Pass-Through Chamber 106 (Hand-off only) (6)PVD Titanium/Titanium Nitride (Process Module 103B, 103C, or 103F) (7)Central Pass-Through Chamber 106 (Hand-off only) (8) Load Lock 107A or107B (9) Loading Station 115A or 115B (wherever the wafer's cassette is)

Another way of depositing an adhesion layer of titanium and a barrierlayer of titanium nitride on a wafer is illustrated with reference tothe system 100 of FIG. 10B and the wafer transfer path of Table 6. Awafer is transferred from a loading station 115, to a load lock 107, andthen to a degas module (intermediate process module 104A or 104B). Fromthe degas module, the surface of the wafer is prepared in a pre-cleanmodule (process module 103A). Thereafter, the wafer is transferred to aPVD titanium module (process module 103G), where an adhesion layer oftitanium is deposited on the wafer. The wafer is then transferred to theback-end by placing the wafer in pass-through chamber 106. In the system100 of FIG. 10B, pass-through chamber 106 is only used as a hand-offlocation for transferring the wafer between load chamber 116 andtransfer chamber 117, and accordingly is not configured as a coolingstation. Further, transfer chamber 117 in this embodiment is capable ofHi-Lo operation. From pass-through chamber 106, the wafer is transferredto a CVD titanium nitride module (process module 103B, 103C, or 103E) inthe back-end. There, a layer of titanium nitride is deposited on thewafer by CVD. From the CVD titanium nitride module, the wafer istransferred to pass-through chamber 106 for hand-off, and transferredback to its cassette on the loading station 115 via a load lock 107. Thewafer is cooled in the load lock 107 while the load lock is vented toatmosphere.

TABLE 6 WAFER TRANSFER PATH FOR THE SYSTEM OF FIG. 10B (1) LoadingStation 115A or 115B (2) Load Lock 107A or 107B (3) Degas Module(Intermediate Process Module 104A or 104B) (4) Pre-Clean (Process Module103A) (5) PVD Titanium (Process Module 103G) (6) Central Pass-ThroughChamber 106 (Hand-off only) (7) CVD Titanium Nitride (Process Module103B, 103C, or 103E) (8) Central Pass-Through Chamber 106 (Hand-offonly) (9) Load Lock 107A or 107B (10) Loading Station 115A or 115B(wherever the wafer's cassette is)

A method, system, and associated apparatus for high throughputsemiconductor processing applications have been disclosed. Whilespecific embodiments have been provided, it is to be understood thatthese embodiments are for illustration purposes and not limiting. Manyadditional embodiments will be apparent to persons of ordinary skill inthe art reading this disclosure. Thus, the present invention is limitedonly by the following claims.

1. A wafer processing system comprising: a load lock having a pedestalconfigured to lift a single wafer from a plurality of pins to supportonly the single wafer during a pump down of the load lock, the pedestalbeing an only wafer support located within the load lock, the load lockhaving an integral cooling unit for cooling the single wafer, the loadlock being separated from a load chamber by a closeable opening thatfaces a vacuum robot in the load chamber; a transport module having theload chamber, a transfer chamber, and a pass-through chamber locatedbetween the load chamber and the transfer chamber, the load chamberbeing coupled to the load lock; an intermediate process module coupledto the load chamber and the transfer chamber; a loader configured toreceive a removable cassette containing a plurality of wafers to beprocessed; an atmospheric robot configured to transfer a wafer betweenthe load lock and the loader, the atmospheric robot being underatmospheric pressure during normal operation; a first set of processmodules coupled to the load chamber; and a second set of process modulescoupled to the transfer chamber.
 2. The system of claim 1 wherein aprocess module in the first set of process modules includes a pre-cleanmodule.
 3. The system of claim 1 wherein a process module in the firstset of process modules includes a physical vapor deposition module. 4.The system of claim 1 wherein a process module in the first set ofprocess modules includes a chemical vapor deposition module.
 5. Thesystem of claim 1 wherein a process module in the second set of processmodules includes a pre-clean module.
 6. The system of claim 1 wherein aprocess module in the second set of process modules includes a chemicalvapor deposition module.
 7. The system of claim 1 wherein a processmodule in the second set of process modules includes a physical vapordeposition module.
 8. The system of claim 1 wherein the intermediateprocess module is configured as a CVD module.
 9. The system of claim 1wherein the intermediate process module is configured as a degas module.10. The system of claim 1 wherein the pass-through chamber is configuredas a cooling station.
 11. The system of claim 1 wherein the intermediateprocess module is configured as a pre-clean module.
 12. The system ofclaim 1 wherein the intermediate process module is configured as a PVDmodule.
 13. A wafer processing system comprising: a load lock havingonly one pedestal for supporting a wafer thereon during a pump down ofthe load lock, the pedestal having only one wafer support for supportingonly one wafer at a time, the pedestal being configured to lift a waferfrom a plurality of pins, the load lock being separated from a firstchamber by a closeable opening; a transport module having the firstchamber, a second chamber, and a pass-through chamber between the firstchamber and the second chamber, the first chamber being coupled to theload lock by way of the closeable opening; a loader configured toreceive a removable cassette containing a plurality of wafers to beprocessed; a first robot configured to transfer a wafer between the loadlock and the loader, the first robot being under atmospheric pressureduring normal operation; an intermediate process module coupled to thefirst chamber; a first process module coupled to the first chamber; asecond process module coupled to the second chamber; a second robotconfigured to transfer a wafer between the load lock and thepass-through chamber, the second robot being under vacuum during normaloperation in the first chamber and facing the closeable opening; and athird robot configured to transfer a wafer between the pass-throughchamber and the second process module, the third robot being undervacuum during normal operation.
 14. The system of claim 13 wherein thepedestal is water-cooled.
 15. The system of claim 13 wherein theintermediate process module is also coupled to the second chamber. 16.The system of claim 13 wherein the pass-through chamber is configured asa cooling station.